Joint detection (JD) or symbol-level interference cancellation (SLIC) may be deployed in a wireless communication system (e.g., long term evolution (LTE)) by identifying interference parameters at a serving user equipment (UE), including their ranks, precoding indices, and modulation orders, etc. For example, when channel reference signal (CRS) related transmission modes (TMs) are used, knowledge of precoding indices is required to estimate an effective channel matrix of interference.
A received signal may be expressed as in Equation (1) as follows:y=HSWSxS+HIWIxI+n  (1)where the subscripts, S and I, indicate a serving signal and a dominant interfering signal respectively. For example, a dominant interfering signal is expressed and other interfering signals are combined into a noise vector. Using Equation (1), an interference rank, i.e., a number of columns in WI, can be determined. Once the interference rank is determined, a matrix of WI is selected from a set of candidate precoding matrices.
If the rank of interference is 1, then there are four candidate precoding matrices.
If the rank of interference is 2, then there are 2 candidate precoding matrices.